JPH0484486A - Ultraviolet area semiconductor laser and semiconductor element and those manufacture - Google Patents

Abstract

PURPOSE:To get a new ultraviolet area semiconductor laser, an LED, and other each kind of semiconductor elements by using the heterojunction structure comprising the crystal layer of ZB structure consisting of the elements of the second cycle and the crystal layer of chalcopyrite structure. CONSTITUTION:In a semiconductor wafer, which has the heterojunction of BeCN2/BN, a BSP layer 12 as a buffer layer is formed on a beta-SiC substrate 11, and a BN layer 13 is formed hereon as the first compound semiconductor crystal layer, and hereon a BeCN2 layer 14 is formed as a second compound semiconductor crystal layer, in order. The substrate 24 stored is heated by a high frequency coil 25, and necessary gas is introduced and blown onto the substrate 26, whereby desired crystal growth can be gotten. The material gas introduced at this time is heated by a heater 26 as occasion demands, and is preliminarily decomposed.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Field of Industrial Application) The present invention relates to a semiconductor device using a novel compound semiconductor material, and in particular to a semiconductor laser capable of emitting light up to the ultraviolet region and its manufacture. Regarding the method.

(Conventional technology) In order to construct a high-speed and high-density information processing system,
The realization of short wavelength semiconductor lasers is desired. The following three conditions are required for a semiconductor material to realize a short wavelength semiconductor laser: 1) It must be a direct transition type, 2) It can form a pn junction, and 3) It can form a heterojunction. A conventionally known semiconductor material that satisfies all of these conditions is InGa.
There is ARP. If this InGaAjJP-based material is used, laser oscillation up to 580 nm is possible.

In order to obtain a semiconductor laser with a shorter wavelength, U-Vl group nitrides, which have a band gap of 3 eV or more and are direct transition type, are being considered as promising materials. However, so far, there has been no success with II-Vl group nitrides because conductivity control has not been achieved. In particular, despite strong demand, materials for semiconductor lasers that oscillate in the ultraviolet region with wavelengths shorter than 300 nm have high potential for application as excitation light sources for various phosphors, light sources for photochemical reactions, etc. Not considered.

Materials for ultraviolet semiconductor lasers are required to have different characteristics from conventional materials for lasers in the near-infrared to visible range because their emission energy is 5 eV or more, which is close to the energy of chemical bonds.

That is, it is necessary that its crystal structure is not damaged by the photon energy of emitted light. For this purpose, in addition to having a wide bandgap, it is desirable that the crystal have a small ionicity and a strong lattice. The importance of this is evident from the fact that it is often observed that alkaline nolides, which are ionic crystals with a wide band gap, are colored by producing defects called color centers when irradiated with ultraviolet light.

Semiconductor materials that have a band gap value of 5 eV or more and that have the possibility of controlling conductivity are limited to a very small number of materials such as GaA, pN system, cubic c-BN, and diamond. Among these, although c-BN and diamond have a band gap of 6 eV or more, they tend to become graphite-like substances with SP2 coordination, which is extremely difficult to synthesize, and they are indirect transition types. The problem is that no other suitable material has been found to combine with this to form a heterojunction. Although the GaA11N system is a direct transition type, it is limited to mixed crystals with a fairly large 8Ω composition, and is a highly ionic crystal with weak bonds compared to the band gap, so crystal defects are likely to occur and the conductivity is poor. Control is extremely difficult. Furthermore, there is a high possibility that defects will be generated by the high-energy light emission.

(Problems to be Solved by the Invention) As described above, the band gap required to realize a semiconductor laser that emits light in the ultraviolet region is, for example, 4 to 5.
Until now, there has been little suggestion of the possibility of a semiconductor material that satisfies the conditions of being sufficiently large eV, capable of pn control, and sufficiently strong and undamaged even with the energy of the emission wavelength.

The present invention was made in view of the above points, and an object of the present invention is to provide a semiconductor element having a heterojunction constructed using a novel compound semiconductor material, and a method for manufacturing the same.

Another object of the present invention is to provide an ultraviolet semiconductor laser constructed using such a new compound semiconductor material and a method for manufacturing the same.

[Structure of the Invention] (Means for Solving the Problems) The semiconductor element and ultraviolet semiconductor laser according to the present invention include:
A first compound semiconductor crystal layer made of a combination of a plurality of elements selected from the second period of the periodic table, and a second compound semiconductor crystal layer made of a combination of a plurality of elements selected from the second period of the periodic table. It is characterized by having a heterojunction with.

Furthermore, in manufacturing such a semiconductor element and an ultraviolet semiconductor laser, the present invention uses materials such as BN and BeCN2.
The first, which is originally difficult to take SP3 coordination. A step of forming a second compound semiconductor crystal layer on a substrate or buffer layer having a stable SP3 coordination such as BP by chemical vapor deposition using a raw material compound having an SP3 orbital to form a heterojunction. It is characterized by having the following.

(Function) Conventionally, substances composed of elements in the second period of the periodic table, such as BN, tend to take SP2 coordination and become glaite-like layered substances, and the desirable SP3 coordination crystals are:
It has been thought that this occurs only at extremely high temperatures and pressures. However, according to research conducted by the present inventors, it has been found that epitaxial growth of c-BN having SP3 coordination, which has been considered extremely difficult in the past, is possible by appropriately selecting a substrate and a growth method.

In other words, if even a part of the substrate has SP2 coordination, the surface has a π-electron-like structure, and there is inevitably SP2 on this surface.
It is easy to form π bonds, which is a characteristic of coordination, and in the end the whole becomes S.
This results in P2 coordination.

However, when a zinc blende (ZB) type crystal with stable SP3 coordination like BP is used as a substrate, the σ bonds are inherently unstable due to the strong bonding force of the σ bonds on the surface. A strong σ bond is formed between B or N even under such conditions, and by repeating this one after another, a ZB type crystal having SP3 coordination grows. This phenomenon is particularly noticeable when the growth method is a chemical vapor deposition method in which surface reactions play an important role, and when the raw material itself is a hydride or organometallic with SP3 coordination. This method uses elements in the first row (Be, B) that tend to take SP2 coordination.

It is similarly applicable to the growth of crystals containing C, N).

Next, a combination material is required that forms a heterojunction with the BN layer having SP3 coordination obtained in this way. B
Since N has the shortest lattice constant among all substances, lattice matching is limited to BeO and diamond, which are also elements in the second period. Of these,
Since BeO is extremely ionic, there is almost no possibility of controlling the conductivity. Furthermore, diamond has almost the same band gap as BN and is of indirect transition type.

However, what is important for the formation of a heterojunction is the
It is considered that the dimensional lattice shape and lattice constant match, and that the bulk lattice constant and lattice shape match is not necessarily required. Therefore, the degree of freedom of the lattice in the direction perpendicular to the heterointerface remains. As such a crystal type, there is a chalcopyrite type crystal, which is a type of tetragonal crystal. A chalcopalite-type compound crystal consisting of elements in the first period has not been reported so far. This is thought to be because it naturally tends to take SP2 coordination and becomes a graphite-like layered material, or because it becomes a cubic mixed crystal under high temperature and high pressure. However, according to a method similar to the above-mentioned BN growth, it should be possible to synthesize a chalcopyrite-type compound composed of a second period element having SP3 coordination even under extremely high temperature and high pressure conditions. In fact, according to the inventor's experiments, a substance with the composition BeCN2 was synthesized, and this
It was confirmed by line diffraction and reflection spectrum measurements that it was a chalcopyrite type crystal having the same electronic configuration as BN. Moreover, the bandgap of this material is slightly smaller than that of BN due to perturbation in the C-axis direction, and a heterojunction can be formed with BN.

Next, in order to use the BeCN2 crystal layer as an active layer, it is necessary that it be of indirect transition type. According to the present invention, this problem can also be solved as follows. First, since BeCN2 synthesized by the method of the present invention is of chalcopyrite type, the conduction band valley, which should originally exist at the same point X as BN, is folded back and overlaps with F.

This was confirmed by reflection measurements. However, this band structure belongs to a type called a quasi-direct transition type, and is essentially a forbidden transition. Therefore, when the vibrator has low strength and is used in an active layer, a low oscillation threshold cannot be obtained.

However, this problem can be solved, for example, by employing a quantum well structure. The application of quantum wells to the active layer as a method of threshold reduction has been reported in the GaAlA
Attempts have been made using s-based infrared semiconductor lasers. Among these, the effect of converting carriers into excitons by increasing the binding energy of excitons by up to four times has been expected. However, in ordinary m-V group bioconductors, the exciton binding energy is 511
1e■, and its effectiveness at room temperature is questionable. However, in the semiconductor made of elements in the second period according to the present invention, due to the nature of atomic potential, the effective mass of electrons is extremely heavier than in the ■-V group semiconductor made of elements in other periods, and its value is about the same as that of holes. reach. For this reason, the binding energy of excitons, which is approximately proportional to the converted masses of electrons and holes, has increased from about 6 g+eV in GaAs to 60 se, which is about 10 times
It becomes larger by about V.

In particular, when used in the well layer of a quantum well, the quantum effect reaches four times as high as 200 meV, and excitons exist in a sufficiently stable manner even at room temperature.

Generally, the luminous efficiency of a light emitting device can be improved by adding a rare earth element or a transition metal element to the light emitting layer. However, since rare earth elements and transition metal elements emit light through transition in the inner core, excitation efficiency is extremely low when injecting electrons and holes, which are interband transitions.
This has been revealed from research on the P system. However, it has been found that in the material made of the second period element according to the present invention, the energy of interband transition is transferred to the core electrons with extremely high efficiency. Rare earths are located at the bottom of the periodic table and have low electron affinity, which is the ability to attract electrons.

However, the elements in the second period have extremely large electron affinities compared to the elements in other periods, and due to this difference, the injected carriers form excitons bound to the rare earth atoms. Because the bound excitons are localized, they have a very large oscillator strength, and the energy of the excitons is transferred to the core electrons of rare earth atoms with high efficiency. For this reason, conventional GaAs, I
Unlike the case where a rare earth element is added to an nP-based material, highly efficient light emission is achieved.

These effects are particularly noticeable in elements such as Ce, which emit light at the transition between the r and d nuclei, and whose interactions with the surroundings are larger than those that emit light at the transition within other r nuclei. be.

As described above, according to the present invention, an ultraviolet semiconductor laser can be realized using a new material.

Furthermore, the material of the present invention can be applied not only to semiconductor lasers but also to various heterojunction devices such as petrojunction transistors to obtain devices that operate stably even at high temperatures.

(Example) The present invention will be explained in detail below.

FIG. 1 is a semiconductor wafer having a B e CN 2 /BN heterojunction according to an embodiment of the present invention. In this example, β-5iC substrate 1
1, a BP layer 12 is formed as a buffer layer, a BN layer 13 is formed as a first compound semiconductor crystal layer, and a BeCN layer 13 is formed as a second compound semiconductor crystal layer.
Two layers and 14 layers are sequentially formed.

FIG. 2 shows a metal organic chemical vapor deposition (MOCVD) apparatus used to manufacture this heterojunction semiconductor wafer.

In the figure, 21 is a reaction vessel made of quartz, and gas introduction pipes 22 (221 to 22
4) is provided.

A graphite susceptor 23 is placed inside the container 2, and a substrate 24 is placed thereon. A high frequency coil 25 for heating the substrate is provided on the outer periphery of the container 2.

A filament-shaped heater 26 (261 to 264) is provided at the outlet of each source gas introduction pipe 22, respectively. There is an exhaust port 27 in the lower part of the container 21, which is evacuated by a rotary pump (not shown), and the pressure inside the reaction container is maintained at a predetermined value by a throttling valve provided in the middle.

Using such an MOCVD apparatus, desired crystal growth is performed by heating the housed substrate 24 with the high-frequency coil 25, introducing necessary raw material gas, and spraying it onto the substrate 26. The raw material gas introduced at this time is heated by the heater 26 and preliminarily decomposed as necessary.

Specific growth conditions and procedures will be explained below. The raw material gas used was dimethyl beryllium (DMBe).

Triethyl boron (TEB) or diborane (B2H6)
, trimethyl gallium (TMGa), phosphine (P
H3), ammonia (NH3), carbon tetrachloride (CCρ4
) or methane (CH4). The substrate temperature is 850~
1150℃, pressure 0.3 atm, total flow rate of raw material gas 10
w1n, and the gas flow rate was set so that the growth rate was 1 μm/h.

For example, the raw material gas flow rate is 1×10− for DMBe and TMG.
6sol/win, CC94 is 5 x 10-5m
ol/sin.

CH4 is 1 x 10-'mol/win, P H
3 is 5 X 10-'l1lol/win, NH
, is I x 10-3 mol/win.

When CH4 was used as a carbon raw material, the filament was energized and heated to about 2000°C.

When each layer obtained was examined by X-ray diffraction, it was found that BN crystal has a ZB structure and B e CN has a chalcopyrite structure.
Reflections corresponding to two crystals were obtained. In addition, the prepared Be
As a result of Hall measurement, the CN2 crystal layer has a carrier concentration I
It was revealed that the crystal showed n-type conductivity of about By mixing and growing silane gas as raw materials, it was possible to control p-type and n-type conduction, respectively.

When optical absorption measurements were performed on the B e CN 2 crystal layer, absorption began to occur when the optical energy was around 5.3 ev, and the square root of the absorption coefficient was proportional to the optical energy. From this relationship, it was found that this crystal has a direct transition gap of about 5.5 eV. However, the value of its absorption coefficient is about 10 3 to 10'cm-' (about 1/10 of the normal value), indicating that it is not a true direct transition type. By excitation by a KrF laser with a wavelength of 225n-,
Emission of 40 n■ was observed, but its intensity was relatively weak and its half-width was as wide as 200 meV. The lattice constant is a~3.6 in the direction perpendicular to the C axis, and the (
111) surface and is almost lattice matched. However, in the C-axis direction, it is C~7.0λ, which is slightly smaller than twice a.

By using the heterojunction wafer shown in FIG. 1 in the manner described above, it is possible to form not only semiconductor lasers in the ultraviolet region but also elements such as heterojunction transistors.

FIG. 3 shows an example in which quantum wells are formed for the purpose of improving luminous efficiency. On the β-5iC substrate 31, a BP buffer layer (0.5 μgo) 32. BN barrier layer (0.5um
)33. B e CN2 well layer (2OA) 34, B
N barrier layers (0,5μ) 35 are sequentially formed. The crystal growth method is the same as in the previous example.

Emission in the ultraviolet region was observed by excitation with an ArF laser (193 nm).

4 and 5 show the relationship between the thickness of the well layer 34, the emission wavelength, and the intensity. When the well layer thickness becomes thinner than 50 nm, the wavelength becomes shorter, and when the well layer thickness is 10 nm, it is approximately 21.5 nm.
Luminescence of the layer was obtained. The luminescence intensity increased rapidly when the well layer thickness became thinner than 50 layers, reached a maximum when the well layer thickness was 15 to 25 layers, and rapidly decreased when the layer thickness was less than that. The shortening of the emission wavelength and the increase in the intensity are due to quantum effects, but this phenomenon occurs only at well layer thicknesses that are considerably thinner than in the case of conventional materials. This is thought to reflect the mass.

The reason why the emission intensity suddenly decreases when the well layer 34 becomes thinner than 15 layers is considered to be because fluctuations in the quantum well width can no longer be ignored.

FIG. 6 shows the relationship between the well layer thickness and the full width at half maximum of light emission. 1
When the well layer thickness is 5 to 25 people, a significant sharpening of the spectrum is observed. This phenomenon is observed only at temperatures as low as liquid nitrogen in conventional materials such as GaA and QAs. This means that B e CN 2 /
This shows that excitons are stable even at room temperature in the BN system.

FIG. 7 shows a semiconductor unit according to another embodiment of the present invention. In this example, a BN layer 73 is formed on the β-5iC substrate 7 through a BP buffer layer 72 with a thickness of 0.5 am,
A B e CN2 layer 74 is grown to a thickness of 0.5 μm. B
e The CN2 layer 74 is doped with Ce, which is a rare earth element. By excitation with an ArF laser (193t+m), strong light emission near 325r+am was observed, indicating that high light emission efficiency is also possible with this method.

In this manner, these embodiments provide a heterojunction structure which has a sufficiently large bandgap and is suitable for use in ultraviolet semiconductor lasers that are not damaged by ultraviolet light.

Next, an example in which the present invention is applied to a specific element will be described.

FIG. 8 shows an example of an LED using a Be CN 2 crystal layer as a light emitting layer. A Si-doped n-type β-5iC substrate 81 is coated with an S1-doped n-type BP buffer layer 82 of about 2 layers.
μl of Si-doped n-type BN2971 is grown on top of this.
layer (carrier concentration 1 x 10 "am-') 83 to approx. 3
As a light emitting layer, about 0.5 utn of non-doped BeCN2 layer 84 and about 2 µl of Be-doped p-type BN cladding layer (carrier concentration IX10''cs-3) 85 are sequentially grown.

Crystal growth was performed using a MOCVD apparatus shown in the tJ2 diagram. In electrodes 36 and 87 are provided on both sides of the element wafer, respectively.

When a chip of 0.3+ am square was cut out from the formed wafer and energized, a current of 70-^ flowed at an applied voltage of about 8 V, and light emission with a wavelength of 225 nm was observed.

FIG. 9 shows an LED of an embodiment in which the light emitting layer is doped with the light emitting center to improve the light emitting efficiency.

Almost similar to the embodiment shown in FIG. 8, an n-type β-5iC substrate 91
, a Si-doped n-type BP buffer layer 92, and an S
i-doped n-type BN2971 layer (carrier concentration lXl0
17■-3) 93, B e CN2 layer 94 as a light emitting layer
．． Be-doped p-type BN cladding layer (carrier concentration I
In electrodes 96.97 are formed on both surfaces by sequentially growing In electrodes 96.95. B which is a light emitting layer
The e CN 2 layer 94 is doped with Ce as a luminescent center. Trisunclopentadienylcerium Ce (C5Hs) 3 was used as the Ce raw material.

In the LED element of this example, light emission of 325 r+m was obtained under the current conditions of 3 V and 70 wA. Note that in this structure, although the emission intensity is slightly lowered, the BN layer may be doped with Ce to serve as a light emitting layer.

Figure 10 shows an example LE using quantum wells in the light emitting layer.
It is D. An n-type β-5iC substrate 101, a Si-doped n-type BP buffer layer 102, and a Si-doped n-type BN2971 layer (carrier concentration I
) 103, and on top of this, a non-doped layer with a thickness of 100
People (BN). 5(B e CN2 ) o, s barrier layer 104 made of mixed crystal, non-doped BeCN with a thickness of 20 people
Quantum well layer 105 with two crystal layers, non-doped thickness 10
0 people (BN) 0. A barrier layer 106 made of (BeCN2)0.5 mixed crystal is successively formed. Furthermore, p on top of this
Type BN cladding layer (carrier concentration I
cm-3) 107 and In electrodes 108 on both sides.
．． 109 is formed. This element also has the MOC shown in Fig. 2.
It is formed using a VD device.

With the structure of this example, fairly strong light emission with a wavelength of 220 nm was obtained under current conditions of 8V and 7mA. In the structure of this embodiment as well, it is conceivable to dope the well layer with Ce.

FIG. 11 shows an example of a DB laser. As in the previous embodiment, the MOCVD apparatus shown in FIG. 2 is used. n
On the type SiC substrate 111, an n-type BP buffer layer (Si doped, I x 1017 cm-3)]]2 of 0.5
On top of this is an n-type BN clad layer (Si-doped,
2X 10"cm-')
μ port, further on top of this is a p-type BN cladding layer (Be-doped,
2X1017(!Il+-') 115 was grown to 1μ. On the p-type cladding layer 115, there is a central width of 5μ
A current blocking layer 116 made of a 5i02 film is formed by the CVD method except for the striped portion of the current blocking layer 116. Further, an A u / B e electrode 118 is formed as a p-side electrode on this layer, and an n-side electrode is formed on the n-substrate 111 on the opposite side. A u/G as electrode
An e-electrode 10 is deposited.

The obtained wafer was separated to produce a laser device with a cavity length of 500 μI. Nox width 10 μS at liquid nitrogen temperature
When driven at a duty ratio of 10-3, an exponential increase in light emission output was observed at a peak current value of 5 A or more, confirming laser oscillation. Note that the oscillation wavelength was approximately 220 nm.

FIG. 12 shows an embodiment in which a quantum well structure is introduced into the active layer portion of FIG. 11. Quantum well structure and growth method is the 10th
This is similar to the LED embodiment shown in the figure. That is, in the light emitting layer part, the non-doped thickness is 100 nm (BN) 0.5 (
B e CN2 ) 0. Barrier layer 1141 made of mixed crystal
Quantum well layer 114□ made of BeCN2 crystal layer with non-doped thickness of 20λ, non-doped thickness of 100 people (BN)
0.5 (B e CN2). , a barrier layer 1143 made of a mixed crystal is sequentially formed.

In this example, a quantum effect appeared as in the case of the LED, and a laser beam of 21 Or+m was observed when a current of 2 A was applied under the same pulse drive conditions as in the above example at a liquid nitrogen temperature. In particular, laser operation was possible even at room temperature, and laser oscillation of 220 nω was observed at a pulse peak value of 5 A.

FIG. 13 is also a modification of FIG. 11, in which the active layer 11
The portion 4 is doped with Ce, which is a rare earth element. The Ce concentration was about I×1010l80', and the growth method was the same as the embodiment shown in FIG. In this example, Ce
Laser oscillation of 325 nm due to internal transition of Atsuko was observed at room temperature, and the operating current at this time was a peak value of approximately IA.
Met.

By the way, B e CN 2 /BN according to the present invention
In the system quantum well, excitons exist stably even at room temperature.

Because excitons behave as quasiparticles with electrically neutral integer spin, they can travel relatively long distances and can be aggregated at high densities without special efforts. A new laser structure can be considered that takes advantage of this feature.

FIG. 14 shows an example of a semiconductor laser in which the oscillation section and the current injection section are separated by utilizing such characteristics. n-type SiC
An n-type BP buffer layer 142 (Si-doped, I x 10 "cm-') is formed on the substrate 141 by 0.5 utb, n
Type BN cladding layer 143 (Si doped, 2X10"■-
3) for 1μ play, p type (BN) 0.5 (B e C
N2) 0.5 barrier layer 144 (Be doped, I
x 10 l8cm-3) for 100 people, undoped B
20 eCN2 quantum well layers 145, n-type (BN) 0
．． 5 (B e CN2 ) 0.5 barrier layer 146 (
Si-doped, I x 1018 cm-3) at 100
Then, a non-doped BN cladding layer 147 of 1 μm was sequentially grown. On top of this, 51 stripes with a width of 10 μm are placed.
A p-type cladding layer 148 is formed by forming a 02 film 149 and selectively diffusing Mg using this as a mask. The p-side A u / B e electrode 151 is connected to the n-type cladding layer 1
48, and the n-side is entirely covered with Au/
A Ge electrode 150 is formed.

When a chip with a resonator length of 500μ layer was cut out from this wafer and energized, 225nm from the central stripe part was cut out.
g laser light was observed.

The separation of the current injection section and the oscillation section in the structure of this embodiment is explained as follows. When electricity is applied, holes are released from the n-type cladding layer 148 and electrons are released from the n-type cladding layer 143, respectively.
g is injected into the well layer immediately below the diffused cladding layer and combines to form excitons. On the other hand, a strong internal electric field is formed in the well layer 145 due to the space charges of the impurity-doped barrier layers 144 and 146, so that the effective band gap of the well layer 145 is reduced.

Since this space charge is shielded from the current-carrying portion where electrons and holes are injected, the band gap reduction effect is weakened. As a result, the effective bandgap of the well layer 145 is smaller in the portion under the central striped SiO2 film 149 than in the periphery. therefore,
Excitons formed at the periphery rapidly condense into the striped area at the center. Since there are no free carriers that cause light absorption in the striped portion where excitons are aggregated, extremely highly efficient light amplification is performed. Absorption by free electrons in the n-type cladding layer is generally smaller than that in the p-type, so it is not considered here.

In this embodiment, the n-type cladding layer 143 is doped in a --like manner, but the striped portion under the surface of the light emitting part is formed by, for example, growth under light irradiation or selective doping using an ion beam, molecular beam, etc. It is also conceivable to do n-type doping. Of course, a similar method may be used for the p-type rad layer portion. Furthermore, in order to change the band gap between the light-emitting part and the current-carrying part, the composition or film thickness of both may be changed. Furthermore, by changing the drive currents of the plurality of electrodes, the position of the light emitting part can be changed significantly. This variation is extremely large, reflecting the long distance that excitons travel, and is expected to have many applications.

The lasers of each of the embodiments described above have operated stably for more than 1000 hours under pulsed operation.

In LED operation, light was stably emitted for more than 2000 hours, and the decrease in brightness was less than 20%. After being energized for a long time,
When observing the light emission pattern of the light emitting part, many dark spots were observed, but the concentration corresponded to threading dislocations in the shrimp layer after growth. Therefore, in the material according to the present invention, the conventional Ga
Unlike materials such as A11As-based materials, it is thought that dislocations and the like do not move or multiply during operation. This fact is considered to be due to strong σ bonds between elements in the second period.

FIG. 15 shows an embodiment in which the present invention is applied to a heterojunction transistor. An n-type BN collector layer 153 is formed on the n-type SiC substrate 151 via the n-type BP buffer layer 152.
A p-type B e CN 2 base layer 154 and an n-type BN emitter layer 155 are sequentially formed. The growth of these crystal layers is performed using the MOCVD apparatus shown in FIG. 2, as in the previous embodiments.

An emitter electrode 156 is formed on the BN emitter layer 155, a base electrode 157 is formed on the Be CN2 base layer 154 exposed by etching, and a collector electrode 158 is formed on the back surface of the substrate.

Since the heterojunction transistor according to this embodiment uses a material with a particularly large band gap, it operates stably even at high temperatures.

The present invention is not limited to the above embodiments. In the embodiment, exclusively B
Although a N/BeCN2 heterojunction is used, other combinations of elements in the second period of the periodic table, such as a diamond/LiBO2 heterojunction, may also be used. As the substrate, for example, GaP or the like can be used in addition to SiC.

If GaP is used as the substrate and the substrate is removed after the necessary crystal growth, a longer life can be expected because the distortion due to lattice mismatch is removed. Also, as a buffer layer, BP
In addition to this layer, it is possible to use a superlattice layer of BN and BP with a different average composition, a (BN) (BP)la mixed crystal layer, or the like.

[Effects of the Invention] As described above, according to the present invention, by utilizing a heterojunction structure consisting of a ZB structure crystal layer made of second-period elements and a chalcopyrite structure crystal layer, ultraviolet region Various semiconductor devices such as semiconductor lasers and LEDs can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a compound semiconductor wafer according to one embodiment of the present invention, FIG. 2 is a diagram showing an MOCVD apparatus for manufacturing the wafer, and FIG. 3 is a diagram showing a compound semiconductor wafer according to another embodiment. , FIG. 4 is a diagram showing the emission wavelength characteristics of the quantum well obtained in the example, FIG. 5 is a diagram also showing the emission intensity characteristics, FIG. 8 is a diagram showing an example in which the present invention is applied to an LED. FIG. 9 is a diagram showing an example of an LED in which the light emitting layer is doped with Ce. Figure 10 shows an example of an LED in which a quantum well is applied to the light emitting layer, Figure 11 shows an example in which the present invention is applied to a DB relay, and Figure 12 shows an example in which a quantum well structure is used in the active layer. Figure 13 shows an example of a DH laser in which the active layer is doped with Ce. Figure 14 shows an example of a DH laser in which the current injection part and the oscillation part are separated. , FIG. 15 is a diagram showing an embodiment in which the present invention is applied to a heterojunction transistor. 11.31,71,81,91,101,l Yu 1
, 14 Yu, 15 Yu...SiC substrate,
Ko 232.72, 82, 92, 102.11214
2.152...BP buffer layer, 13,3335.7
3...BN crystal layer, ], 4.3474...BeCN
2 crystal layer, 21... Reaction vessel, 22... Raw material gas introduction pipe, 23... Susceptor, 24... Substrate, 25...
RF coil, 26... Heater, 27... Exhaust port, 8
3.93,103.113 143...n-type BN crystal layer, 84,94,114,145...BeCN2 crystal layer, 85,95,107,115°147...p-type B
N crystal layer, 104.105114+, I 143
”-(BN) (BeCN2) mixed crystal barrier layer,] 05,
1142”-BeCN2ii child well layer, ]53...
n-type BN collector layer, 154... p-type BeCN2 base layer, 155- n-type BN emitter layer. Figure 1 Applicant's representative Patent attorney Takehiko Suzue Figure 2 Well layer Q Atsumori Figure 7 Figure 14 Figure Zheng) LOgu

Claims (12)

[Claims] (1) A first compound semiconductor crystal layer made of a combination of multiple elements selected from the second period of the periodic table, and a second compound made of a combination of multiple elements selected from the second period of the periodic table. An ultraviolet semiconductor laser characterized by having a heterojunction with a semiconductor crystal layer. (2) The ultraviolet semiconductor laser according to claim 1, wherein the first compound semiconductor crystal layer is BN, and the second compound semiconductor crystal layer is BeCN_2. (3) The BN has a zincblende crystal structure, and the B
3. The ultraviolet semiconductor laser according to claim 2, wherein eCN_2 has a chalcopyrite crystal structure. (4) The first and second compound semiconductor crystal layers include S
2. The ultraviolet semiconductor laser according to claim 1, wherein the ultraviolet semiconductor laser is formed on a substrate or a buffer layer having P^3 coordination. (5) The buffer layer may be a BP layer, a superlattice layer of BN and BP with a changed average composition, or (BN)_a(BP)_
5. The ultraviolet semiconductor laser according to claim 4, wherein the ultraviolet semiconductor laser is a 1_-_a mixed crystal layer. (6) a substrate; a first compound semiconductor crystal layer made of a combination of a plurality of elements selected from the second period of the periodic table formed on this substrate via a buffer layer; and a first compound semiconductor crystal layer formed on this crystal layer a second compound semiconductor crystal layer made of a combination of a plurality of elements selected from the second period of the periodic table, which becomes a quantum well layer; and the first compound semiconductor crystal formed on this crystal layer. An ultraviolet semiconductor laser comprising: a third compound semiconductor crystal layer made of the same material; and a third compound semiconductor crystal layer made of the same material. (7) The semiconductor laser according to claim 6, wherein the substrate is a semiconductor crystal substrate having SP^3 coordination. (8) The buffer layer is a BP layer, a superlattice layer of BN and BP with a changed average composition, or (BN)_a(BP)_1
7. The ultraviolet semiconductor laser according to claim 6, wherein the ultraviolet semiconductor laser is a ___a mixed crystal layer. (9) The first and third compound semiconductor crystal layers are zinc blende type BN, and the second compound semiconductor crystal layer is chalcopyrite type BeCN_2. Ultraviolet semiconductor laser. (10) The ultraviolet semiconductor laser according to claim 6, wherein the current injection section and the oscillation section are formed spatially separated. (11) A first compound semiconductor crystal layer made of a combination of a plurality of elements selected from the second period of the periodic table, and a second compound semiconductor crystal layer made of another combination of a plurality of elements selected from the second period of the periodic table. 1. A semiconductor device characterized by having a heterojunction with a compound semiconductor crystal layer. (12) A method for manufacturing a semiconductor device having a heterojunction consisting of a first compound semiconductor crystal layer and a second compound semiconductor crystal layer, the method comprising: depositing a chemical vapor phase on a substrate or a buffer layer having SP^3 coordination; forming a first compound semiconductor crystal layer having an SP^3 coordination made of a combination of a plurality of elements selected from the second period of the periodic table by a growth method; and on the first compound semiconductor crystal layer. , forming a second compound semiconductor crystal layer having an SP^3 coordination made of a combination of a plurality of elements selected from the second period of the periodic table by a chemical vapor deposition method. A method for manufacturing a semiconductor device.